effects of forces on the motion of objects. The magnitude of the change in motion can be calculated using the rela- tionship F = ma, which is independent of the nature of the force. Whenever one object exerts force on another, a force equal in magnitude and opposite in direction is exerted on the first object. Physical Science: Conservation of energy and the increase in disorder

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All energy can be considered to be either kinetic energy,

which is energy of motion; potential energy, which depends on relative position; or energy contained by a field, such as electromagnetic waves.

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Everything tends to become less organized and less or-

derly over time. Thus, in all energy transfers, the overall effect is that the energy is spread out uniformly. Examples are the transfer of energy from hotter to cooler objects by conduction, radiation, or convection and the warming of our surroundings when we burn fuels. Life Science: The cell

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Most cell functions involve chemical reactions. Food

molecules taken into cells react to provide the chemical constituents needed to synthesize other molecules. Both breakdown and synthesis are made possible by a large set of protein catalysts, called enzymes. The breakdown of some of the food molecules enables the cell to store energy in specific chemicals that are used to carry out the many functions of the cell. Life Science: Matter, energy, and organization in living sys- tems

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As matter and energy flows through different levels of

organization of living systems cells, organs, organisms, communities and between living systems and the physi- cal environment, chemical elements are recombined in dif- ferent ways. Each recombination results in storage and dissipation of energy into the environment as heat. Matter and energy are conserved in each change. Science in Personal and Social Perspectives: Personal and